Psoriatic arthritis… an often-missed diagnosis

Psoriatic arthritis is a distinct disease, different from rheumatoid arthritis and ankylosing spondylitis- another common type of arthritis- but sharing similar features to each. The disability and functional impairment in psoriatic arthritis can be as severe as that occurring from rheumatoid arthritis.

Typically, a patient will have had psoriasis for a number of years before the arthritis develops. A small proportion of patient will develop the arthritis concurrently with the skin disease and an even smaller percentage will develop the skin disease after the joint disease.

Psoriatic arthritis may affect most joints in an oligoarticular pattern, meaning a few scattered joints are affected and the joint inflammation does not have the symmetrical pattern seen in rheumatoid arthritis. Enthesitis, which is inflammation of the tendons that attach to bone, is common in psoriatic arthritis. “Sausage digits” – swelling of the fingers and toes so that they look like little sausages is frequent. Nail changes are also common. These include “pitting” and separation of the nail from the nailbed. Some patients will develop carpal tunnel syndrome because of inflammation in the wrist. Inflammation of the eyes is a serious complication, as is involvement of the aortic valve of the heart.

Joint deformity is frequent and affects 40% of patients with the disease. Psoriatic arthritis has a significant impact on quality of life. The skin disease is a tremendous burden and often leads to depression.

The inflammatory process that causes both the skin disease as well as the joint disease is driven by elevated levels of a substance called tumor necrosis factor, or TNF.

A patient with psoriasis who complains of joint pain, swelling, morning stiffness, and fatigue should raise a high level of suspicion for the diagnosis of psoriatic arthritis.

Laboratory testing will show evidence of inflammation and imaging procedures such as magnetic resonance imaging (MRI) can help confirm the diagnosis.

Treatments that improve the skin disease do not necessarily improve joint symptoms and vice versa.

Treatment goals include symptomatic relief and control of disease progression.

Non-steroidal anti-inflammatory drugs are helpful for relieving some symptoms. However the majority of patients with psoriatic arthritis will require a combination of methotrexate or sulfasalazine and anti-TNF biologic therapy. Anti-TNF therapies have provided a significant advance in the treatment of both the skin as well the joint disease in patients with psoriatic arthritis.

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